In the previous sections we reviewed the measurements of the abundances probing a fraction of the IGrM volume. As pointed out early by [1]} the physically meaningful quantity for the study of the IGrM (and of the ICM) are the metal (iron or other chemical elements) mass and stellar mass present in the groups (and clusters). The ratio of the iron mass and stellar mass is directly linked to a fundamental quantity in chemical evolution models, the iron (or other chemical elements when measured) yield which is the ratio of the total iron mass released by stars to the total stellar mass formed for a given stellar population
[2]}, [3]}, [4]}:
\(\mathcal {Y}_{\rm Fe} = \frac{M^{\rm star}_{\rm Fe,500} + M_{\rm Fe,500}}{M_{\rm star,500}(0)} ,\) 
